also looks similiar to my problem, but my network freezes up and i need to reboot or replug the network cable in order to make it work. I'm swedish btw, ^^
Looks like a client disconnecting. Does it give you any problems or just the error message, but nothing bad happens?
nothing bad happens everything works fine its just popping up error messages some times, not so often can i ignor it?
I think those error messages are when the players leave Minecraft without using the disconnect button, meaning they just close the window. I've tried this using my own client to connect to my server, and I can reproduce the error message when I just hit the X button to close the minecraft window, but nothing bad happens to the game itself.
basically, the server expects a certain sequence of events when a player disconnects.. when that doesn't happen, next time it tries to update the player, it gets told that the connection is gone.. which throws an error (which you see).. the server then enters the disconnect routine for that player and cleans up and gets on w/ life